Wagner cast iron dating
However, since it was registered with the US Patent Office in 1909 as an actual trademark, it would seem that the term "trademark" or "TM" would be preferable to "logo" More info on the Griswold TM at THIS LINK .
Also, sizes started to be marked in "inches" instead of in trade numbers or "No." numbers. Some new patterns and styles were developed including the Griswold "Hearthstone" pieces under General Housewares (GHC).The earliest of the cookware was marked ERIE for the Pennsylvania city it was made in.ERIE iron remains among the finest of Griswold’s foundry products.Sometimes incorrectly called Smoke Ring, Fire Ring, or another name, none are correct since the heat ring has nothing to do with smoke or fire.Griswold called what we collectors have named "heat ring" just "rim" or "rimmed bottom" in their early catalogs.